1. Field of the Invention
The present invention relates to a cleaning solution for cleaning resist patterns of a semiconductor device and a cleaning method using the same. More particularly, the present invention relates to a cleaning solution for cleaning impurities in the surface portion of the silicon germanium (SiGe) layer of a semiconductor device and a cleaning method using the same.
2. Description of the Related Arts
The trend in the art requires integration of semiconductor devices with lower power consumption in order to process a greater amount of information faster. Therefore, the art requires that the size of the semiconductor devices be lowered to 100 nm or less, thereby reducing the space for forming patterns.
In particular, the development of transistors in CMOS devices requires fine gate structure and thin film gate. Also, the development of highly integrated devices and the operation thereof requires low power consumption. Technical improvement is necessary and the cost investment thereof increases commensurate with the small size of the transistors.
Therefore, to develop a MOS-type transistor that requires low power, a method of improving the driving power independent of the transistor's small size has been suggested. This method includes a layer of silicon germanium between the silicon substrate and the silicon layer.
According to the above-mentioned method, a silicon germanium layer is formed on the silicon substrate and then a strained silicon layer with tensile transformation is formed. The strained silicon layer is used as a transistor channel to improve the driving power of the transistor. That is, as disclosed in a literature (IEDM Tech. Digest, 1994, p 373-376), the strained layer in which tensile transformation may occur and positioned on the silicon germanium layer, exhibits an improved migration because the practical effective mass of electrons converts to light when compared with that of the general silicon substrate. The transistor having this property exhibits an improved transistor driving power.
In addition, as the size of the semiconductor device decreases, the increased electron mobility and the shield of leakage current that leaks to the lower portion of the substrate from the source/drain region of the semiconductor devices are very important considerations for driving the highly integrated semiconductor devices.
When the leakage current that leaks from the source/drain region is formed on the semiconductor substrate to the lower portion of the substrate, the total amount of the leakage current from the semiconductor devices is fairly large, thereby lowering the driving velocity of the semiconductor devices. Accordingly, there is an ongoing effort to use the buried insulation layer of the silicon germanium layer formed on the semiconductor device to prevent the leakage current from flowing to the lower portion of the substrate.
The buried insulation layer that corresponds to the silicon germanium layer is positioned under the lower portion of the active region of the substrate, and prevents the migration of the electrons to the lower portion when a channel is formed in the semiconductor device and the electrons migrate at the source/drain region. The substrate, including silicon germanium, is obtained by forming a silicon germanium layer on the silicon substrate and growing silicon on the silicon germanium layer.
The silicon germanium layer that is formed is selectively present at the active region of the semiconductor substrate by an isolation process on the semiconductor substrate. To form a semiconductor device that includes the silicon germanium layer requires a cleaning process for removing impurities or particles generated during the evaporation process of the silicon germanium layer and the etching process. Here, the cleaning process is preferably carried out by using a cleaning solution having a high etching selectivity with respect to the silicon germanium layer to remove the impurities.
Generally, standard cleaning 1 (SC-1) cleaning solution is most widely used. By wet etching using SC-1, the etching selectivity onto silicon germanium with respect to silicon can be advantageously controlled according to the temperature and time applied. However, the surface portion of the silicon germanium layer is rapidly oxidized due to hydrogen peroxide (H2O2) or hydrogen fluoride (HF) in the SC-1. Because of the oxidation of the silicon germanium layer, silicon germanium is etched faster than the common silicon layer.
Therefore, the SC-1 cleaning solution should not be used for the cleaning process of removing particles present at the exposed substrate of the silicon germanium layer. In addition, certain other cleaning solutions for cleaning semiconductor substrate, including hydrogen fluoride and nitric acid, should also not be used because they oxidize and over-etch the silicon germanium layer.
Japanese Laid-Open Patent Publication No. Hei 15-086554 discloses a manufacturing apparatus for a semiconductor substrate and a method of manufacturing a semiconductor substrate by which a chemical cleaning method ensures the removal of impurities from the surface of a silicon germanium layer. The apparatus includes a first cleaning bath containing a first pure water, a second cleaning bath containing hydrogen fluoride, and a third cleaning bath containing a second pure water. The substrate having a silicon germanium layer as a surface layer, is subsequently cleaned through the first, second and third cleaning baths using water or hydrogen fluoride. Small particles in the air and a natural oxide layer present at the silicon germanium layer can be effectively removed. However, the surface portion of the silicon germanium layer may be damaged even though the native oxide layer present at the surface of the silicon germanium layer is effectively removed.
As described above, various methods for treating a semiconductor substrate including silicon germanium are used. However, when a cleaning solution containing hydrogen fluoride, hydrogen peroxide or nitric acid is used for cleaning a semiconductor substrate in which the silicon germanium layer is exposed, the surface portion of the exposed silicon germanium layer that is exposed to the cleaning solution may damage and the shape of the surface portion thereof may deform. That is, a cleaning solution for silicon germanium and a method of cleaning thereof overcoming the above-described method may be required.